Electronic balances in many cases are calibrated by means of an internal calibration weight. To perform a calibration, a calibration weight of a specifically defined mass is brought into force-transmitting contact with the force-transmitting device that is arranged in a force-measuring cell of a balance, whereupon a reference value is determined. Based on this reference value, further weighing parameters of the balance can be adjusted. After the calibration has been performed, the contact between the calibration weight and the force-transmitting device is released again, and the calibration weight is secured in a rest position. In the foregoing process, the calibration weight is moved from a rest position into a calibration position and back to the rest position by a transfer mechanism. In the calibration position, the calibration weight is in force-transmitting contact with the force-transmitting device; in the rest position there is no force-transmitting contact. In many balances, the calibration weight arrangement and the force-transmitting device are arranged behind one another, as disclosed in commonly-owned U.S. Pat. No. 6,194,672 to Burkhard.
There are a diversity of transfer mechanisms for moving a calibration weight which, when in its rest position, in most cases rests on a holder that is connected to a lifting system.
A calibration weight arrangement is disclosed in commonly-owned U.S. Pat. No. 5,148,881 to Leisinger with a calibration weight that is moved vertically by wedges arranged in pairs which slide horizontally against each other, whereby the calibration weight is brought into force-transmitting contact with the force-transmitting device of the balance. This transfer mechanism is driven by a motor through a spindle that is connected to the wedges.
A likewise vertical lifting and lowering of a calibration weight is achieved by a device that is described in Burkhard '672. The weight rests on a holder which is moved by an electrically driven transfer mechanism.
It is important for the calibration weight to be securely immobilized, primarily in the rest position, even in the presence of shocks, hard knocks, or if the balance is dropped, so that the calibration weight is not abruptly brought into contact with the force-transmitting device and thereby causes damage to the lever mechanism. The transfer mechanisms of the known state of the art secure the calibration weight by simply pressing it as firmly as possible against a fixed stop, an arrangement which protects the calibration weight only against falling out of its holder as a result of a shock or a fall to the floor which could occur for example while the balance is being transported. If an abrupt force acts on the calibration weight, it will be directly passed on to the transfer mechanism, whereby the latter could even be destroyed.
Consequently, the object to be accomplished is to create a calibration weight arrangement with a transfer mechanism that not only keeps the calibration weight immobilized in case the balance is hit, shocked or dropped, but also provides protection by absorbing and redirecting a suddenly attacking force.